ABSTRACT
U-invariant closed subspace A subspace of the representation space of a unitary representation U that is invariant under each of the unitary operators Ug .
Ulm factor A quotient group, Gα/Gα−1, of an Abelian p-group G, where α is less than the type of G and the Gα are defined by transfinite induction with G1 equal to the elements of G of infinite height. See type of a group.
